1. Field of the Invention
The present invention relates to a squeegee apparatus of a liquid electrophotographic printer.
2. Description of the Related Art
As shown in FIG. 1, a liquid electrophotographic printer such as a color laser printer includes laser scanning units (LSUs) 50 for forming a latent electrostatic image of an image to be developed on a photoreceptor belt 10 by irradiating a laser beam onto the photoreceptor belt 10, development units 20 for developing the latent electrostatic image into a predetermined image using a developer liquid having a liquid solvent mixed with a powdered toner, a drying unit 30 for drying and removing the liquid solvent remaining on the image after development, and a transfer unit 40 for printing the image developed on the photoreceptor belt 10 on a sheet of printing paper (S).
Here, each of the development units 20 includes a development device having a development roller 21, a cleaning brush 24 and a developer liquid supply nozzle 23, and a squeegee apparatus having a squeegee roller 25, a squeegee backup roller 26 and an air spray nozzle 27. The squeegee apparatus squeegees the imaging region of the developed image to remove excess developer liquid therefrom. The excess developer liquid which is not used for development is removed from the photoreceptor belt 10 by the squeegee apparatus.
If the excess developer liquid is not sufficiently withdrawn from the photoreceptor belt 10 by the squeegeeing action of the squeegee roller 25, the operation load of the drying unit 30 is increased. Also, since the image which is not completely dried may migrate to the transfer unit 40, a clean image quality cannot be obtained. Thus, the overall printing quality is influenced by the efficiency of removing the excess developer liquid by the squeegee roller 25, that is, the squeegeeing efficiency.
The squeegeeing efficiency varies with the temperature of the photoreceptor belt 10. When the photoreceptor belt 10 is heated at a temperature of 40 to 45.degree. C., the squeegeeing efficiency is highest. In the printer having the above-described construction, since the photoreceptor belt 10 contacts the respective heated rollers in the drying unit 30 and the transfer unit 40 while the printing operation is carried out, the photoreceptor belt 10 appears to be kept at a high temperature. However, in practice, the photoreceptor belt 10 is rapidly cooled by the heat exchange with the developer liquid while passing through the development units 20 and the contact with the squeegee roller 25, the development backup roller 22 and the squeegee backup roller 26. Thus, it is difficult to keep the photoreceptor belt 10 at a temperature higher than 30.degree. C. while squeegeeing.
Therefore, in order to attain an optimum squeegeeing efficiency, there is an increasing demand for means for keeping a photoreceptor belt at a high temperature while a squeegeeing operation is carried out.